Not exactly...
Your variable DistanceSoundBomb changes from 0 (complete silence) to 1 (full volume).
If distance between objects is 1000 pixels or more, then it will be 0.
You can change "1000" in that formula to 50 or whatever number you want.
For playing/stopping sound you should use these events:
System->Compare two values -> distance(detector.x, detector.y, bomb.x, bomb.y) is less than 50 -> Play sound
System->Compare two values -> distance(detector.x, detector.y, bomb.x, bomb.y) is greater than 60 -> Stop sound